Natural resources such as gas, oil, and water residing in a subterranean formation or zone are usually recovered by drilling a wellbore into the subterranean formation while circulating a drilling fluid in the wellbore. After terminating the circulation of the drilling fluid, a string of pipe (e.g., casing) is run in the wellbore. The drilling fluid is then usually circulated downward through the interior of the casing and upward through the annulus, which is located between the exterior of the pipe and the walls of the wellbore. Next, cementing is typically performed whereby a cement slurry is placed in the annulus and permitted to set into a hard mass (i.e., sheath) to thereby attach the casing to the walls of the wellbore and seal the annulus.
During the development and life of a hydrocarbon recovery well drilling, completing, servicing, and treating operations are routinely carried out. During these routine procedures, it is often necessary to seal one or more zones in the well from other zones, either temporarily or permanently. Often a packing system, having a plugging tool and a packing element will be used to create the desired zonal isolation.
A plugging tool is typically lowered into a cased oil or gas well and set at a desired location inside or outside the casing string to provide zonal isolation in the well. A packing element is carried by the plugging tool and is the structure to which physical force is applied so that a seal may be created. The packing element is caused to conform to the space between two adjacent zones in the wellbore and seal the well or formation. Retrievable plugs are used during drilling and workover operations to provide a temporary separation of zones. Permanent plugs are used to permanently close off the well, for example, above a lower zone or formation.
Commonly, when a lower zone has become non-productive but one or more upper zones remain productive, a through tubing bridge plug may be installed by lowering the bridge plug through the casing string on a conveyance such as a wireline, coiled tubing or the like and then setting the plug by axially compressing the packing elements of the bridge plug to expand them into contact with the inner surface of the casing to provide a seal. Once in the sealing configuration, a significant pressure differential can be created across the plug.
Likewise, during cementing or production, it may be desirable to seal one or more zones in the annular region of the wellbore between the casing string and the formation (wellbore wall). External casing packers may be deployed into the annular region between the casing string and the wellbore wall to seal one zone from an adjacent zone. The plug may again be set by axially compressing the packing elements of the packer to expand them into contact with the outer surface of the casing and the wellbore wall to provide a seal.
A variety of packing elements are known in the art and elastomeric packing elements have found favor because of their ability to conform and provide a dependable seal. Elastomeric packing elements may take different configurations, for example, they may be swell packers or pressure packers or inflatable packers or compression packers. Varied packer configurations allow selection of an appropriate packer material and expansion method that is suited to the wellbore to be sealed.
Generally, swell packers respond to hydraulic fluid pressure by expanding to fill the available space in the annulus or within the casing string. Swell packers are known to suffer from extrusion problems at high differential pressures which may result in seal loss. Accordingly, anti-extrusion devices have been developed to prevent extrusion of the elastomeric material at high differential pressures thereby minimizing seal loss. Prior anti-extrusion systems have included collar systems and petal assembly systems configured to hold the elastomeric packing material in place, see for example, U.S. Pat. No. 7,938,176. Such systems have proven to be either incapable of preventing extrusion or have been very complex causing issues relating to deployment or device reliability.
Prior anti-extrusion systems have used an expanding assembly to prevent extrusion. The assembly is generally equipped with a series of slots forming a series of petals that when protracted cover the end of the packing element. While these petal assemblies improve extrusion losses, they do not prevent them, as the slots used to form the petals leave gaps between the individual petals resulting in some elastomeric material extrusion. Overlapping petal assemblies have been described, e.g., a second expanding assembly of petals configured to overlap with a first set of petals and cover the gaps left by the first set of petals. Providing plugging tools with multiple expanding petal assemblies have heretofore required complex interlocking, multi-layer hinge mechanisms.